U.S. Pat. No. 4,016,053 discloses a system for distributing alumina to smelting pots. The system is based on air-activated gravity conveyors, i.e. fluidized bed conveyors, in which the alumina is fluidized by a vertical, upwardly directed air stream. Gravity thereby makes the alumina flow like a liquid, via fluidized bed transport ducts, to the smelting pots.
The air used for fluidizing the alumina in the conveyors is allowed to exit from the transport ducts, and is transported, together with the reduction process flue gases from the smelting pots, to a gas cleaning plant, which generally comprises filters, e.g. of bag filter type.
The gas cleaning plant consumes a lot of energy, partly because of the high pressure difference required to transport the dust laden gas through the bag filters.